204 DISEASES OF THE ROSE, 



forming brown cocoons. The perfect moths appear the following 

 June. The wings measure, when expanded, about an inch across. 

 First pair, tawny yellow, with a deep, broad band across the 

 centre ; second pair, pale, dull yellow, with darker margins." — 

 Paxtofi. 

 35. Argya antiqua. Common Vaporer Moth. " This moth does no 

 injury to the rose-trees, although the caterpillars are found upon 

 them in great numbers." — Paxton. 



A most destructive enemy of the Rose is a small insect of the 

 genus Tenthredo, respecting which very little is knowTi. Dr. 

 Merat, a French writer, describes it in detail, which description 

 we translate from his pamphlet, in the hope that it may be of 

 some assistance to those who are inclined to investigate the habits 

 of the various insects which infest the R?»se. 



DESTRl'CTIOX OF GROWING ROSES BY THE LARV.i OF A FOUR-WIN'GED INSECT OP 

 THE ANCIENT GENUS TENTHREDO, BY DR MERAT. 



By Dr. Merat. 



The malady of rose-trees which I am about to make known has been nowhere 

 described. Scarcely any traces of it can be found in authors, although known, by 

 its ravages, to professed gardeners and some Rose amateurs. That which I am 

 now about to publish is the result of five years' observation made in my own 

 garden. 



In the month of April, if the temperature .should happen to reach twelve or 

 fifteen degrees of Reaumur, insects which are supposed to be flies, hover around 

 the rose-trees then just beginning to sprout. They alight on the growing leaves, 

 make an opening at the arm-pit of one of them by the use of a kind of saw 

 (whence the name of sav;-Jly), Avhich the female thrusts from the extremity of her 

 abdomen, and deposits in it an egg, or more probably a living worm (the manner 

 of the carnivorous fly). As soon as this is done, this larva, almost imperceptible 

 at first, is seen to excavate a hole and making lodgment in it. to extend a small 

 passage, in a downward direction, into the stem of the future Rose, which passage 

 it enlarges in length and size, and then makes its egress through another opening, 

 which it makes in the lower part of the passage. 



The appearance of the saw-fly does not occur at the same time every year. It 

 always coincides with the first budding of the rose-tree. It is evident, that if ic 

 should occur before that time, the fl)'^ would perish for want of food, and without 

 leaving ofispring, an accident contrary to the economy of nature. If the develop- 

 ment of the rose-trees were too far advanced, the insect, which is very weak, could 

 not penetrate the sprouts, on accotmt of their having become too hard, and it 

 could not, therefore, leave offspring. 



I note here the date of the appearance of these insects in five different years : 

 In 1840, it happened on the 5th day of May; in 1841, the 25th of April; in 1842, 

 the 15th of April; in 1843, the 3d of April. Respecting this last and very early 



